1. Field of the Invention
This invention relates to a paper web threading apparatus for a rotary printing press for threading a paper web through a paper web threading path extending from a paper web supply section through a printing section to a folding section to thereby conduct printing of the paper web, and more particularly to a paper web threading apparatus for effective use in a printing press having a paper web threading path which extends from a paper web supply section through a plurality of guide rollers and turning bars including a double ender device and a bay window device to a folding section, the arrangement being made such that the threading of a paper web is conducted by a paper web threading member adapted to be moved on and along a guide provided along a paper web threading path.
2. Description of the Prior Art
A prior art paper web threading apparatus for a rotary printing press is publicly known from, for example, the apparatus disclosed in Japanese Laid-Open Patent Application NO. HEI-1-103647. This prior art paper web threading apparatus comprises pipe-shaped guide rails provided with branched portions along a plurality of paper web threading paths and having a longitudinally extending slit formed on one side thereof, the guide rails each having notches formed at appropriate intervals therealong; driving units provided in the notches; running members adapted to be driven by the driving units so as to run on their respective guide rails in zigzag direction and having full length somewhat longer than the spacing between the notches; each of the running members having a clip secured thereto and adapted to detachably hold a paper web connecting adaptor connected to the cleading end of printing paper drawn out from a paper web roll disposed at a paper web supply section.
The above-mentioned prior art has posed the following problems.
Threading of a paper web in a rotary printing press is made from the upstream side of a paper web threading path to the downstream side thereof, namely, from a paper web supply section to a folding section. In this case, the paper web to be threaded along the path is guided by a comparatively short running member (which is referred to as short running member hereinbelow). In this case, since the driving members for driving the short running member are provided at intervals somewhat shorter than the length of the short running member, the short running member is driven by two sets of driving units along some part of the path, and by one set of driving units along the other part thereof so that the driving force exerted on the running member cannot be kept constant. Further when the short running member is passing through corners where the resistance to the running thereof is high, it is, decelerated by high friction thus causing unevenness in the running speed thereof so that the speed of the paper web connected to the short running member becomes uneven. As a result, in the course of threading of a paper web through a paper web threading path which requires reliability, such troubles such as, for example, slackening of paper web due to deceleration and formation of creases thereof, and also severance of paper web etc. have occurred.
Further, in case of printing newspaper, for example, the recent increases in pages and color-printing have required provision of a number of guide rollers and turning bars including double ender means and bay window means along a paper web threading path extending from a paper web supply section to a folding section, which resulted in considerable increase in the length of the paper web threading path as compared with that in the past. As a result, because the driving units for driving the short running member movable on the guide rail are provided at intervals somewhat shorter than the length of the short running member, it has become inevitable to provide larger member of driving units. Provision of a multiplicity of driving units not only increases the cost of printed matters, but also complicates the narrow interior of the frame of the rotary printing press, and also renders it difficult to carry out ordinary printing operation as well as maintenance/repairs and inspection, thus causing problems in terms of safe operation.